Shellac composition containing dicyandiamides



Patented Aug. 6, 1935 UNITED STATES PATENT OFFICE,

SHELLAG COMPOSITION CONTAINING DICYANDIAMIDES No Drawing. Application October 22, 1932,

Serial No. 639,039

3 Claims. (01. 2 60-2) This invention relates to an improved composition of matter incorporating a resin, shellac being preferred, methods of producing it, and improved articles made therefrom. The princi- 5 pa] object of this invention, though by no means confined to it, is to form a hard composition which can be used for plastic mouldings or for protective purposes, such as coatings, that has a fusion or softening point considerably higher than compositions that have been prepared from the same base materials.

It is well known that shellac belongs to the heat convertible type of resins, and affords one of the best materials for a base in plastic com- 15 positions for moulding purposes. Moulded articles prepared from shellac are the best known insulators for very high voltage service. One disadvantage in the use of shellac is the fact that most of its products have relatively low temperatures of fusion or softening under the application of heat, which is a marked disadvantage when certain engineering and safety features are considered.

According to my invention, I employ an ammono-dicarbonic acid added to the resinous material, shellac in the example below, and subject the same to heat, or heat and pressure, according to the product desired, in order to form a binding or a base material or a hard, resistant object, for example, a moulded object, the point of fusion of which is substantially raised over the resin in its original form.

Improved shellac compositions have been prepared by the addition of certain so-called hard- 1,673,805; 1,673,806; 1,673,807; 1,673,808). It is believed these agents, such as guanidines, alde-' hyde ammonia, aminonaphthalene, aromatic secondary amines, and phenols form condensation products with shellac. The exact chemical mechanism is unknown. It is, however, clear and can readily be confirmed that these compounds are limited to about one per cent (1.0%) in the effective amounts which can be used. The maximum amount in no waycorresponds chemically to any known total number of chemical group or groups in shellac. Hence, the degree of improvement which can be obtained by such chemicals is decidedly limited in their range of ing uses, such compositions are unable to meet the demands. The ammono-dicarbonic acid employed by me is dicyandiamide, having two or more chemically active groups and enabling im- 5 proved properties by increasing the proportion ening agents (U. S. Patents 1,673,803; 1,673,804;

effect, and for certain aforementioned engineer-= many times in excess of the limit of about one per cent (1.0%) of the agents specified in the aforementioned patents. Dicyandiamide may be incorporated by solution in alcohol as in the case with the agents specified in the said patents, 5 but it also can be mixed with the shellac in powdered form and uniformly incorporated by means of hot rolls, or other suitable means.

As an example of my invention in which the valuable agent is added in the production of 10 an improved moulding compound, is as follows:

A mixture of nine pounds of asbestos, three pounds of shellac and two ounces dicyandiamide is repeatedly passed and repassed between hot rolls maintained at a. temperature sufiicient to keep the shellac in the composition molten. When the mixture in thismanner has been rendered uniform in distribution, the resulting plastic mass may be pressed into slabs, or so-called biscuits of any desired type or shape. These biscuits may then, if desired, be subjected to a heat curing or baking process. The exact details and conditions of any such intermediate step will, to a large extent, depend upon the nature and service to which the later manufactured article is to be put. This product may then be placed in a mould either in biscuit (by softening on a steam table) or in a powdered form, and subjected to required heat and pressure necessary for forming a hard, insoluble, less fusible object. Where a limited amount of agent and previous heat treatment of the biscuit material has been employed, it may be necessary to cool the mould during the pressing operation. The moulding may take place in a number of ways but good results may be obtained by softening the biscuit material at 300 F., placing a slight excess in the mould and subjecting the same to 2700 pounds per square inch. The pressure is not released until the material has cooled to a temperature sufficiently low to be readily handled without deformation. The heat employed during the said pressure treatment may be 270 F.

It is understood that this example in no way limits the method in which the desirable agent, dicyandiamide, may be added in preparing the composition, nor as to its proportion, the use or manner in which the intermediate baking process is employed, the temperatures and pressure used, nor the use or form which the composition containing dicyandiamide is to be put to service. All these conditions may be varied in order to obtain desired effects without impairing the product. Instead of asbestos, other types of fillers may be employed and suitable coloring agents may be added for specific purposes.

Shellac to which dicyandiamide has been added and subjected to heat may be used as a binding agent for a variety of materials or as a plastic cement. In this application, shellac is taken to include all forms of lac, the secretion of the insect Tachardia lacca Kerr, whether in the raw or refined, or manufactured forms.

It is known that aromatic or cyclic amines can be used as condensing or polymerization agents for resins of the heat convertible type (U. S. Patents 1,342,326; 1,146,388; British Patent 4,154- 1909), J. Ind. Eng. Chem. 17, 225, (1925), and these agents are distinct from the agent employed by me which contains two different active groups as a primary amino group, NH2 and a tertiary amino nitrogen in a nitrile group, C N. As aforementioned, chemicals containing one active group are limited in their field of application.

Having described my invention, what I claim and desire to secure by Letters Patent, is as follows:-

1. A composition of matter formed by the application of heat to shellac and dicyandiamide in proportion to efiect condensation by such heat reaction.

2. A composition of matter capable of hardening on heating, comprising shellac and dicyandiamide.

3. A method of making molding compositions which comprises adding to shellac dicyandiamide and then subjecting the resulting mixture to heat.

WILLIAM HOWLETT GARDNER. 

